Mark InstanceTemplate advanced machine features not Computed

[slevenick]

Fixes: hashicorp/terraform-provider-google#9436

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• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

compute: changed `advanced_machine_features` on `google_compute_instance_template` to track changes when the block is undefined in a user's config

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 2 files changed, 6 insertions(+), 1 deletion(-))
Terraform Beta: Diff ( 3 files changed, 7 insertions(+), 2 deletions(-))

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform Beta: Diff ( 2 files changed, 3 insertions(+), 2 deletions(-))

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceGoogleSQLCaCerts_basic|TestAccDatasourceGoogleServiceNetworkingPeeredDnsDomain_basic|TestAccCloudRunService_cloudRunServiceSqlExample|TestAccCloudFunctionsFunction_vpcConnector|TestAccComputeFirewallPolicyRule_update|TestAccContainerAnalysisOccurrence_multipleSignatures|TestAccContainerCluster_withAddons|TestAccContainerCluster_withWorkloadIdentityConfig|TestAccServiceNetworkingPeeredDNSDomain_basic|TestAccSQLDatabase_sqlDatabaseBasicExample|TestAccSqlDatabaseInstance_basicSecondGen|TestAccSqlDatabaseInstance_basicMSSQL|TestAccSqlDatabaseInstance_settings_basic|TestAccSqlDatabaseInstance_settings_deletionProtection|TestAccSqlDatabaseInstance_slave|TestAccSqlDatabaseInstance_diskspecs|TestAccSqlDatabaseInstance_maintenance|TestAccSqlDatabaseInstance_settings_upgrade|TestAccSqlDatabaseInstance_settingsDowngrade|TestAccSqlDatabaseInstance_authNets|TestAccSqlDatabaseInstance_multipleOperations|TestAccSqlDatabaseInstance_basic_with_user_labels|TestAccSqlDatabaseInstance_withPrivateNetwork|TestAccSqlDatabase_update|TestAccSqlDatabase_basic|TestAccSqlClientCert_mysql|TestAccSqlUser_postgresIAM You can view the result here: https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=213099